In dentistry, a dental impression material that is prepared by mixing a liquid-phase silicone base material with a curing agent is used in order to obtain a dental impression. The impression material is usually received in an impression material cartridge assembly before use thereof. The impression material cartridge assembly includes impression material cartridges which accommodate the silicone base material and the curing agent, respectively, and a mixing tip coupled to the impression material cartridges to mix the materials and to discharge the resulting mixture.
Referring to Korean Patent Registered No. 10-0914836, there is disclosed a conventional coupling structure between impression material cartridges and a mixing tip.
FIG. 1 is a cross-sectional view showing a construction of a conventional mixing tip 10. As illustrated in the drawing, the conventional mixing tip 10 includes a lower casing 11, an upper casing 15 coupled to the lower casing 11, and a mixer 17 rotatably disposed in both the casings. A silicone base material A is introduced through a first flow path 12 formed in the lower casing 11 while a curing agent B is introduced through a second flow path 13 formed in the lower casing 11. Both the materials are mixed with each other at a predetermined mixing ratio by means of a mixer 17, and the resulting impression material C is discharged to the outside.
The conventional mixing tip 10 is constructed such that the silicone base material A and the curing agent B are mixed in a predetermined mixing ratio and then discharged. Since the first flow path 12 and the second flow path 13 have different diameters, upon initial application of the same discharge pressure to the flow paths, the silicone base material A is first discharged for a certain period of time from the first flow path 12 having a larger diameter and the curing agent B is subsequently discharged from the second flow path 13.
Consequently, only the silicone base material A is discharged without discharge of an impression material having a desired mixing ratio for an initial certain period of time after application of an actuation signal. Therefore, the discharge of the impression material involves a cumbersome work in that a user has to discard the initially discharged silicone mixture and to wait for discharge of the impression material mixed at the desired mixing ratio.